Method and System for Power Management in a Frequency Division Multiplexed Network

ABSTRACT

A network device may receive a signal from a headend, wherein a bandwidth of the received signal spans from a low frequency to a high frequency and encompasses a plurality of sub-bands. The network device may determine, based on communication with the headend, whether one of more of the sub-bands residing above a threshold frequency are available for carrying downstream data from the headend to the circuitry. The network device may digitize the signal using an ADC operating at a sampling frequency. The sampling frequency may be configured based on a result of the determining. When the sub-band(s) are available for carrying downstream data from the headend to the network device, the sampling frequency may be set to a relatively high frequency. When the sub-band(s) are not available for carrying downstream data from the headend to the network device, the sampling frequency may be set to a relatively low frequency.

CLAIM OF PRIORITY

This patent application is a continuation of U.S. patent applicationSer. No. 14/015,481, now U.S. Pat. No. 9,049,491, which claims priorityto U.S. provisional patent application Ser. No. 61/695,036 filed on Aug.30, 2012, now expired.

The above-identified documents are hereby incorporated herein byreference in its entirety.

INCORPORATION BY REFERENCE

This patent application also makes reference to U.S. Patent ApplicationPublication Serial No. 2014/0064420 titled “Method and System for PowerManagement in a Network Device Based on Multi-Protocol Detection” andfiled on Aug. 28, 2013, which is hereby incorporated herein by referencein its entirety.

TECHNICAL FIELD

Aspects of the present application relate to communication networks.More specifically, to a method and system for power management in aFrequency Division Multiplexed Network.

BACKGROUND

Existing receivers in FDM networks (e.g., DOCSIS, MoCA) can consume toomuch energy. Further limitations and disadvantages of conventional andtraditional approaches will become apparent to one of skill in the art,through comparison of such approaches with some aspects of the presentmethod and system set forth in the remainder of this disclosure withreference to the drawings.

BRIEF SUMMARY

A method and/or system is provided for power management in a frequencydivision multiplexed network, substantially as illustrated by and/ordescribed in connection with at least one of the figures, as set forthmore completely in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depicts an example communication system in accordance with anexample embodiment.

FIG. 1B depicts portions of an example network device operable toreceive and process cable television/DOCSIS signals in accordance withan example implementation of this disclosure.

FIGS. 2A and 2B illustrate effect of sampling a cable downstream atdifferent sampling frequencies.

FIGS. 3 and 4 depict example low-power cable/DOCSIS sampling schemes inaccordance with an example implementation.

FIG. 5 is a flowchart illustrating an example process for configuring areceiver front-end in accordance with an example implementation of thisdisclosure

FIG. 6 is a flowchart illustrating an example process for configuring areceiver front-end in accordance with an example implementation of thisdisclosure.

FIG. 7 is a flowchart illustrating an example process implemented by aheadend that supports power reduction in customer premise devices.

DETAILED DESCRIPTION

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (i.e., hardware) and any software and/orfirmware (“code”) which may configure the hardware, be executed by thehardware, and or otherwise be associated with the hardware. As usedherein, for example, a particular processor and memory may comprise afirst “circuit” when executing a first one or more lines of code and maycomprise a second “circuit” when executing a second one or more lines ofcode. As utilized herein, “and/or” means any one or more of the items inthe list joined by “and/or”. As an example, “x and/or y” means anyelement of the three-element set {(x), (y), (x, y)}. As another example,“x, y, and/or z” means any element of the seven-element set {(x), (y),(z), (x, y), (x, z), (y, z), (x, y, z)}. As utilized herein, the term“exemplary” means serving as a non-limiting example, instance, orillustration. As utilized herein, the terms “e.g.,” and “for example”set off lists of one or more non-limiting examples, instances, orillustrations. As utilized herein, circuitry is “operable” to perform afunction whenever the circuitry comprises the necessary hardware andcode (if any is necessary) to perform the function, regardless ofwhether performance of the function is disabled, or not enabled, by someuser-configurable setting. Although various exemplary cable/DOCSISembodiments are described herein, aspects of the invention areapplicable to other networks which utilize frequency divisionmultiplexing and/or are coordinated via management messages.

FIG. 1A depicts an example communication system in accordance with anexample embodiment. Shown in FIG. 1 is a terrestrial television antenna102, a satellite dish 104, an Internet Protocol (IP) network 106, aheadend 108, a wide area network (e.g., hybrid fiber-coaxial (HFC)network) 118, a gateways 120 a and 120 b, end systems 126 a and 126 b(e.g., computers), and end systems 128 a and 128 b. The headend 108comprises a switch 110, a video modulator 112, a cable modem terminationsystem (CMTS) 114, and a splitter/combiner 116.

For downstream traffic, the headend 108 may receive television signalsvia the antenna 102 and the satellite dish 104, and may receive data viathe IP network 106. The switch 110 may convey the television signals tothe video modulator 112 and the data to the CMTS 114. The videomodulator 112 may modulate the received television signals onto acarrier. The CMTS 114 may modulate the received data onto a carrier. Thesplitter/combiner 116 may combine the outputs of the video modulator 112and the CMTS 114 resulting in a frequency division multiplexed (FDM)signal comprising one or more television channels and/or one or moreDOCSIS channels. The FDM signal may be onto the wide area network (WAN)118 for distribution to customer premise equipment (CPE). Each customerpremise 130 may comprise one or more network devices operable to receivesignals via the WAN 118, process the signals to recover content carriedtherein, and distribute the content to end systems such as computers126, televisions 128, and/or the like. For example, customer premises130 a comprises a gateway with integrated cable modem 122 a andset-top-box 124 a. The cable modem 122 a and the STB 124 a may share anRx front-end such as the Rx front-end 160 described below in FIG. 1B. Asanother example, customer premises 130 b comprises cable modem 122 b andset-top-box 124 b implemented as separate devices. The cable modem 122 band the STB 124 b may each comprise an Rx front-end such as the Rxfront-end 160 described below in FIG. 1B.

For upstream traffic, one or both of cable modem 122 a and STB 124 band/or one or both of cable modem 122 b and STB 124 b may be operable totransmit, via a Tx front-end not shown, messages to the CMTS 114. Forsuch upstream data, messages (e.g., network management/maintenancemessages) may be modulated onto one or more carriers for transmissionvia the WAN 118. The splitter/combiner 116 may then convey the messageto the CMTS 114. The CMTS 114 may process the messages and, in anexample embodiment, adjust transmission parameters (e.g., modulationparameters, transmit power, frequency offsets, etc.) and/or performother maintenance/management based on the received messages.

FIG. 1B depicts portions of an example network device operable toreceive and process cable television/DOCSIS signals in accordance withan example implementation of this disclosure. The example device may be,for example, an implementation of the gateway 120, the cable modem 122b, or the STB 124 b. The device comprises a receiver front-end 160 anddigital processing circuitry 170. The front-end 160 comprises alow-noise amplifier (LNA) 150, a lowpass filter (LPF) 152, ananalog-to-digital converter (ADC) 154, and a clock generator 156.

The LNA 150 may be operable to amplify signal 148 received via the WAN118. The LNA 150 may be operable to amplify the signal 148 over a rangeof frequencies that encompasses frequency bands used by the applicablestandard/protocol. For example, for a cable/DOCSIS network, the LNA 150may be operable to amplify the range of frequencies ˜50 MHz to ˜1000 MHzshown in FIGS. 2A and 2B.

The filter 152 may be operable to selectively attenuate and/or amplifyfrequency sub-bands of the amplified signal 151. In an exampleimplementation, the filter 152 is a low-pass filter which applies atleast a threshold amount of attenuation (e.g., 3 dB) to frequenciesabove a cut-off frequency, F_(CO). The cut-off frequency (or frequenciesfor a bandpass or multi-band filter) of the filter 152 may bepreconfigured and/or tuned during runtime of the device in which thefront-end 190 resides. The tuning of the filter 152 may be via afeedback loop and/or via one or more control signals (e.g., controlsignal 178 from digital processor 170).

The analog-to-digital converter 154, may be operable to concurrentlydigitize signals over a range of frequencies that encompasses frequencybands used by multiple networks/protocols, such as the range offrequencies ˜50 MHz to ˜1550 MHz shown in FIGS. 2A and 2B. The samplingfrequency used by the ADC 154 may be determined by the signal 172 fromthe clock generator 156.

The clock generator 156 may be operable to generate a clock signal 172that oscillates at a frequency controlled by the digital processor 170via control signal 176. The clock signal 172 may be, for example, asinusoid or a square wave. The frequency clock signal 172 may controlledbe via a feedback loop and/or via one or more control signals. (e.g.,control signal 176 from digital processor 170).

The digital processor 170 may be operable to process (e.g., filter,demodulate, decode, etc.) the digitized signal 155 output by the ADC154. The processor 170 may process the signal 155 to detect whether oneor more channels of the digitized frequency band(s) need to beprocessed. When such channels do not need to be processed, the digitalprocessor 170 may be operable to configure itself, and/or othercomponents of the network device in which it resides, into a lower powermode of operation. A determination of whether or not certain channelsare to be processed (e.g., demodulated, decoded, etc.) may be determinedheuristically (e.g., based on a spectral analysis of the digitizedsignal, on past traffic patterns, etc.) and/or may be based on controlmessages (e.g., UCD, MAP, and/or other MAC management messages definedin DOCSIS standards) that the processor 170 monitors for in thedigitized signal. For channels that are determined to need processing inthe network device, the processor 170 may demodulate, decode, filter,and/or the like to recover data transmitted on the channel(s) and outputthe data as signal 180.

FIGS. 2A and 2B illustrate effect of sampling a cable downstream atdifferent sampling frequencies. In FIG. 2A the sampling frequency issufficiently high that the Nyquist frequency falls outside of the cabledownstream spectrum. In this manner, portions of the cable spectrum donot fold onto itself during digital-to-analog conversion. In FIG. 2B, onthe other hand, the Nyquist frequency falls within the cable spectrumsuch that it folds onto itself during digital-to analog conversion,thereby causing interference in the digitized signal.

FIG. 3 depicts an example low-power cable/DOCSIS sampling scheme inaccordance with an example implementation of this disclosure. FIG. 3shows a cable/DOCSIS system that uses single-carrier QAM channels forcarrying downstream traffic. Each channel may be, for example, 6 or 8MHz. The cable/DOCSIS band spans from F_(lo) (e.g., 55 MHz) to F_(hi)(e.g., 1000 MHz). Conventionally, any of the QAM channels in thecable/DOCSIS band may be selected as a DOCSIS downstream channel.Consequently, to ensure that the DOCSIS downstream channel can besampled without aliasing problems, the sampling frequency is high-enough(e.g., ˜2*F_(hi)) to account for the case where the highest possibledownstream channel is chosen as the DOCSIS downstream channel. Adrawback of this is that a higher sampling frequency typicallycorresponds to higher power consumption.

In an example implementation, selection of the DOCSIS downstream channelmay be limited to channels below a determined threshold frequency F_(T)(e.g., 150 MHz). The cut-off frequency, F_(CO), of the low pass filter152 may then be set to the threshold frequency (or far enough above thethreshold frequency to allow for desired margin) as shown by the idealfilter response depicted in FIG. 3. Accordingly, since the receivingdevice (e.g., gateway 120 or cable modem 122 b) knows (e.g., based onmanagement messages, heuristics, hardware and/or software configuration,etc.) that the DOCSIS downstream will necessarily be below the thresholdfrequency, and that the filter is configured to prevent higher portionsof the cable downstream from folding onto the desired channel 302, arelatively low sampling frequency 304 (e.g., relative to the ˜2 GHzsampling frequency that would be needed to digitize channel N residingat ˜1 GHz). The relatively low sampling frequency may be selected suchthat the Nyqust frequency falls at (or at a frequency just far enoughabove the threshold frequency to allow for desired margin) F_(T). Use ofthe lower sampling frequency 304 may save considerable power in thereceiving device.

In an example implementation, all downstream data may be restricted totransmission on channels below the threshold frequency. In anotherexample implementation, only critical data (e.g., certain MAC managementmessages) may be restricted to channels below the threshold frequencywhile other data may be transmitted on downstream channels above thethreshold frequency. In such an implementation, the non-critical datamay or may not be received by a particular network device depending onhow that device is configured (e.g., a device in a power saving mode maynot be processing the downstream channel on which the non-critical datais received and, thus, may not receive the data).

In FIG. 4, an example sampling technique in an OFDM system (e.g., anext-generation DOCSIS modem) is depicted. Each OFDM sub-band maycomprise, for example, 20 to 50 KHz of bandwidth centered on asubcarrier frequency. In the example embodiment depicted, the networkdevice (e.g., gateway 120 or cable modem 122 b) may only need to receiveMAC management messages (e.g., SYNC, UCD, and/or MAP messages). Forexample no end-systems connected to the receiver are requesting content.Accordingly, by limiting the sub-bands available for carrying suchmanagement messages to sub-bands that lie below a threshold frequencyF_(T), a relatively low sampling frequency 404 may be used (e.g.,relative to the ˜2 GHz sampling frequency that would be needed todigitize sub-band N in FIG. 4). The relatively low sampling frequencymay be selected such that the Nyquist frequency falls at the thresholdfrequency F_(T) (or at a frequency just far enough above the thresholdfrequency to allow for desired margin). The relatively low samplingfrequency may result in lower power consumption. To prevent the lowersampling frequency from causing higher subcarriers from folding onto thedesired subcarrier 402, the filter 152 may be configured to have itscut-off frequency, F_(CO), set to F_(T) (or slightly above F_(T) toallow for desired margin).

FIG. 5 is a flowchart illustrating an example process for configuring areceiver front-end in accordance with an example implementation of thisdisclosure. While the process is described with reference to gateway 120for illustration, the process may be implemented in any network device.The process begins with block 602 in which gateway 120 powers up andestablishes communications with a headend.

In block 504, during ranging/registration with the headend, the gateway120 attempts to determine a frequency, F_(T), that can be relied upon asthe upper bound of channels used for communicating packets that thegateway 120 must necessarily receive. If the headend supports therestricting of necessary information (e.g., MAC management messages) tochannels below a threshold frequency, and a value of the thresholdfrequency is communicated to gateway 120 during ranging/registration,then the process advances to block 510.

In block 510, the processor 170 of the gateway 120 sets the cut-offfrequency of the filter 152 of the gateway 120 to F_(T) plusdesired/necessary margin.

In block 512, the processor 170 of the gateway 120 configures the clockgenerator 156 of the gateway 120 such that the frequency of the clocksignal 172 is 2*F_(T) plus desired/necessary margin.

In block 514, the ADC 154 of the gateway 120 begins digitizing thesignal received from the headend.

Returning to block 504, if F_(T) cannot be determined (e.g., becauserestricting necessary info to channels below a threshold frequency isnot supported by the headend), then the process advances to block 506.

In block 506, the processor 170 of the gateway 120 sets the cut-offfrequency of the filter 152 of the gateway 120 to F_(hi) plusdesired/necessary margin.

In block 508, the processor 170 of the gateway 120 configures the clockgenerator 156 of the gateway 120 such that the frequency of the clocksignal 172 is 2*F_(hi), plus desired/necessary margin.

FIG. 6 is a flowchart illustrating an example process for configuring areceiver front-end in accordance with an example implementation of thisdisclosure. While the process is described with reference to gateway 120for illustration, the process may be implemented in any network device.The process begins with block 602 in which gateway 120 powers up andestablishes communications with a headend.

In block 604, the value of a threshold frequency, F_(T), to be used asthe upper limit for communications to network devices operating in alower power mode is determined. The gateway 120 may negotiate thethreshold frequency or may simply be informed of a threshold frequencydetermined by the headend. In an example implementation, block 604 maytake place during, for example, ranging/registration in a DOCSISnetwork.

In block 606, the gateway 120 determines whether to enter a lower-powermode. As an example, the gateway 120 may enter a lower-power mode when,for example, the computer 126 a is not requesting any downstream dataand when the television 128 a is not consuming any content transmittedon a channel having a frequency above F_(T). If the device determines toenter a lower-power, then the process advances to block 608.

In block 612, the processor 170 of the gateway 120 sets the cut-offfrequency of the filter 152 of the gateway 120 to F_(T) plusdesired/necessary margin.

In block 614, the processor 170 of the gateway 120 configures the clockgenerator 156 of the gateway 120 such that the frequency of the clocksignal 172 is 2*F_(T) plus desired/necessary margin.

In block 616, the ADC 154 of the gateway 120 begins digitizing thesignal received from the headend.

Returning to block 606, if the gateway 120 decides not to enter a lowpower mode (e.g., because the front end is shared between the CM 122 aand the STB 124 b, and the television 128 a is requesting data from achannel that is transmitted above F_(T)), them the process advances toblock 608.

In block 608, the processor 170 of the gateway 120 sets the cut-offfrequency of the filter 152 of the gateway 120 to F_(hi) plusdesired/necessary margin.

In block 610, the processor 170 of the gateway 120 configures the clockgenerator 156 of the gateway 120 such that the frequency of the clocksignal 172 is 2*F_(hi) plus desired/necessary margin.

FIG. 7 is a flowchart illustrating an example process implemented by aCMTS that supports power reduction in customer premise devices. In block702, one or more network devices, such as gateway 120 and cable modem122 b, establish communications with the CMTS.

In block 704, the CMTS determines a threshold frequency F_(T). Thedetermination of F_(T) may be based, for example, on how many devicesare served by the headend, a level of service (e.g., based on type ofsubscription) to be provided to the network devices, and/or the like.For example, where many devices are served by the CMTS, a higher F_(T)may need to be chosen to provide more bandwidth available for allocationto one or more DOCSIS downstream channels, whereas fewer devices maypermit a lower F_(T) and correspondingly less bandwidth available to beallocated to one or more DOCSIS downstream channels.

In block 706, the determined value of F_(T) may be communicated to thenetwork device served by the CMTS, such that the network devices can settheir sampling frequencies accordingly.

In block 708, communications between the CMTS and the network devicestake place. In planning these communications, the headend restrictsdownstream bandwidth allocations to channels below F_(T).

In block 710, if there is a change in the network configuration (e.g.,new network device registers with the CMTS), the process returns toblock 704 and a new value of F_(T) (which may be the same as theprevious value) is determined.

In an example implementation of this disclosure, a network device (e.g.,gateway 120 or cable modem 122 b) may receive a signal from a headend(e.g., cable television/DOCSIS headend 108), wherein a bandwidth of thereceived signal spans from a low frequency (e.g., F_(lo) in FIG. 3) to ahigh frequency (e.g., F_(hi) in FIG. 3) and encompasses a plurality ofsub-bands (e.g., channels 1 through N in FIG. 3 or sub-bands 1 through Nin FIG. 4). The network device may determine, based on communicationwith the headend (e.g., during ranging/registration and/or through MACmanagement messages), whether one of more of the sub-bands residingabove a threshold frequency (e.g., channels above F_(T) in FIG. 3 orsub-bands above F_(T) in FIG. 4) are available for carrying downstreamdata from the headend to the circuitry. The network device may digitizethe signal using an analog-to-digital converter (ADC) (e.g., 154)operating at a sampling frequency. The sampling frequency may beconfigured based on a result of the determining. When the one or moresub-bands are available for carrying downstream data from the headend tothe network device, the sampling frequency may be set to a frequencythat is at least twice the high frequency. When the one or moresub-bands are not available for carrying downstream data from theheadend to the network device, the sampling frequency may be set equalto or substantially equal to (e.g., within a determined tolerance orerror margin of) to the threshold frequency. When the one or moresub-bands are available for carrying downstream data from the headend tothe network device, the sampling frequency may be set to a relativelyhigh frequency. When the one or more sub-bands are not available forcarrying downstream data from the headend to the network device, thesampling frequency may be set to a relatively low frequency.

Continuing with the example implementation, the network device maycomprise a filter (e.g., 152) which may filter the received signal priorto the digitizing. The network device may configure a cut-off frequencythe filter based on the result of the determining. When the one or moresub-bands are available for carrying downstream data from the headend tothe network device, the cut-off frequency of the filter may be set to afrequency that is at least twice the high frequency. When the one ormore sub-bands are not available for carrying downstream data from theheadend to the network device, the cut-off frequency of the filter maybe set to a frequency equal to or substantially equal to (e.g., within adetermined tolerance or error margin of) the threshold frequency. Whenthe one or more sub-bands are available for carrying downstream datafrom the headend to the network device, the cut-off frequency may be setto a relatively high frequency. When the one or more sub-bands are notavailable for carrying downstream data from the headend to the networkdevice, the cut-off frequency may be set to a relatively low frequency.

In an example implementation of this disclosure, a cable modem (e.g.,122 b) may be coupled to a cable modem termination system (CMTS) (e.g.,114) and may comprise an analog-to-digital converter (ADC) (e.g., 154)for digitizing signals from the CMTS. The cable modem may determine(e.g., based on communications with the CMTS) that only a portion of allsub-bands (e.g., channels 1 through N in FIG. 3 or OFDM sub-bands 1through N in FIG. 4) in the DOCSIS frequency band (e.g., from ˜55 MHz to˜1 GHz) are available for communication of DOCSIS downstream data fromthe CMTS to the cable modem, and that the portion of the sub-bandsreside below a threshold frequency (e.g., F_(T) in FIG. 3 or FIG. 4). Inresponse to the determination, the cable modem may configure a samplingfrequency of the ADC to be equal to or substantially equal to thethreshold frequency. The cable modem may digitize a signal received fromthe CMTS using the configured sampling frequency. The cable modem maycomprise a filter (e.g., 152) for processing signals from the CMTS andmay configure a cut-off frequency of the filter to be equal to orsubstantially equal to (e.g., within a determined tolerance or errormargin of) the threshold frequency. Prior to the digitizing of thesignal from the CMTS, the cable mode may filter the signal using theconfigured filter.

Other implementations may provide a non-transitory computer readablemedium and/or storage medium, and/or a non-transitory machine readablemedium and/or storage medium, having stored thereon, a machine codeand/or a computer program having at least one code section executable bya machine and/or a computer, thereby causing the machine and/or computerto perform the steps as described herein for power management in afrequency division multiplexed network.

Accordingly, the present method and/or system may be realized inhardware, software, or a combination of hardware and software. Thepresent method and/or system may be realized in a centralized fashion inat least one computing system, or in a distributed fashion wheredifferent elements are spread across several interconnected computingsystems. Any kind of computing system or other apparatus adapted forcarrying out the methods described herein is suited. A typicalcombination of hardware and software may be a general-purpose computingsystem with a program or other code that, when being loaded andexecuted, controls the computing system such that it carries out themethods described herein. Another typical implementation may comprise anapplication specific integrated circuit or chip.

The present method and/or system may also be embedded in a computerprogram product, which comprises all the features enabling theimplementation of the methods described herein, and which when loaded ina computer system is able to carry out these methods. Computer programin the present context means any expression, in any language, code ornotation, of a set of instructions intended to cause a system having aninformation processing capability to perform a particular functioneither directly or after either or both of the following: a) conversionto another language, code or notation; b) reproduction in a differentmaterial form.

While the present method and/or system has been described with referenceto certain implementations, it will be understood by those skilled inthe art that various changes may be made and equivalents may besubstituted without departing from the scope of the present methodand/or system. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the presentdisclosure without departing from its scope. Therefore, it is intendedthat the present method and/or system not be limited to the particularimplementations disclosed, but that the present method and/or systemwill include all implementations falling within the scope of theappended claims.

1-19. (canceled)
 20. A system comprising: an analog-to-digital converteroperable to digitize a signal received from a headend; a digitalprocessing circuit operable to: determine, based on signals receivedfrom said headend, which one or more of a plurality of sub-bands areavailable for carrying data from said headend to said cable modem; andcontrol a sampling frequency of said analog-to-digital converter suchthat: when one or more of said plurality of sub-bands that are above aparticular threshold frequency are available for carrying data from saidheadend to said cable modem, said sampling frequency is set to afrequency that is twice a highest frequency of said one or more of saidplurality of sub-bands that are above said particular threshold; andwhen said one or more of said plurality of sub-bands that are above aparticular threshold are not available for carrying data from saidheadend to said cable modem, said sampling frequency is set to afrequency that is at least twice said particular threshold frequency.21. The system of claim 20, comprising a filter operable to filter saidsignals received from said headend prior to said digitization of saidsignals by said analog-to-digital converter.
 22. The system of claim 21,wherein a frequency response of said filter is configurable duringruntime of said system.
 23. The system of claim 21, wherein: when one ormore of said plurality of sub-bands that are above a particularthreshold frequency are available for carrying data from said headend tosaid cable modem, a cut-off frequency of said filter is set to afrequency that is twice a highest frequency of said one or more of saidplurality of sub-bands that are above said particular threshold; andwhen said one or more of said plurality of sub-bands that are above aparticular threshold are not available for carrying data from saidheadend to said cable modem, said cut-off frequency of said filter isset to a frequency that is at least twice said particular thresholdfrequency.
 24. The system of claim 20, wherein said data consists ofmanagement messages.
 25. The system of claim 24, wherein said managementmessage comprise one or more of: a DOCSIS SYNC message, a DOCSIS UCDmessage, and a DOCSIS MAP message.
 26. The system of claim 20, whereinsaid digital processing circuit is operable to negotiate said particularthreshold frequency with said headend.
 27. The system of claim 20,wherein said digital processing circuit is operable to determine saidparticular threshold frequency based on communications from saidheadend.
 28. A system comprising: an analog-to-digital converteroperable to digitize a signal received from a headend; a digitalprocessing circuit operable to: determine, based on signals receivedfrom said headend, which one or more of a plurality of sub-bands areavailable for carrying management messages from said headend to saidcable modem, wherein for a first network configuration said managementmessages are restricted to one of more of said plurality of sub-bandsbelow a particular threshold frequency, and for a second networkconfiguration one or more of said plurality of sub-bands above saidparticular threshold frequency are available for carrying saidmanagement messages, and control a sampling frequency of saidanalog-to-digital converter such that: for said first networkconfiguration, said sampling frequency is set to a frequency that is atleast twice said particular threshold frequency; and for said secondnetwork configuration, said sampling frequency is set to a frequencythat is at least twice a highest frequency of said plurality ofsub-bands.
 29. The system of claim 28, comprising a filter operable tofilter said signals received from said headend prior to saiddigitization of said signals by said analog-to-digital converter. 30.The system of claim 28, wherein a frequency response of said filter isconfigurable during runtime of said system.
 31. The system of claim 28,wherein: for said first network configuration, a cut-off frequency ofsaid filter is set to a frequency that is at least twice said particularthreshold frequency; and for said first network configuration, saidcut-off frequency of said filter is set to a frequency that is at leasttwice a highest frequency of said plurality of sub-bands.
 32. The systemof claim 24, wherein said management messages comprise one or more of: aDOCSIS SYNC message, a DOCSIS UCD message, and a DOCSIS MAP message. 33.The system of claim 28, wherein said digital processing circuit isoperable to negotiate said particular threshold frequency with saidheadend.
 34. The system of claim 28, wherein said digital processingcircuit is operable to determine said particular threshold frequencybased on communications from said headend.